General problems encountered in Casting – Casting Defects:
Shrinkage Problems: One of the most common issue that takes notice in Casting.. The casting process should consider the shrinkage of ceramic ware during drying and firing stages. The ceramic ware has to be formed keeping in mind the shrinkage factor and the product should be given dimensions accordingly to address this shrinkage so that the final ware after drying and firing process will be of correct dimension. This factor when not addressed can cause either re-work or scrap. If the ware dimensions are greater after shrinkage then it could be corrected by re-work, if the ceramic ware shrinks too much during drying then it has to be scraped.
Blisters: This is another important defect which can be caused due to improper casting. Blisters are raised or localized swelling occurring on the ceramic ware surface. The Blisters can be formed during casting process. While casting, the air can get entrapped leading to blister formation. Blisters can arise in both means of casting; Slip casting and dry pressing. In dry pressing method, if there is not enough pressure applied on the article to drive out all the entrapped air then blisters may be formed. In Sip Casting method, blisters may be formed if the clay is highly plastic and if no sufficient time is given for drying.
To be Contd….
